Plasticine caterpillars show how birds could protect crops

Although the scent of freshly-cut grass may seem nice, what you're actually smelling is a distress signal. Thanks to a recent-conducted study, scientists from the University of Delaware now believe that such signals could be used to summon insect-eating birds to valuable crops.

It was already known that when plants are in distress, they send out odor cues (aka "plant volatiles") to alert other organisms in the area. As a result, animals such as birds may be drawn to the plants, subsequently eating any insects that are feeding on them. The U Delaware team states that until now, however, no one had tested whether the phenomenon could be harnessed to beneficial effect in an agricultural setting.

Led by Ivan Hiltpold and Greg Shriver, the researchers set up odor dispensers adjacent to corn stalks in an experimental field. Some of those devices emitted a blend of synthetic compounds that simulated plants' distress signals, while others simply contained a neutral organic solvent. On stakes near plants surrounding all of the dispensers, the scientists placed fake caterpillars made from plasticine and orange-colored pins.

It was subsequently found that the caterpillars near the distress-signal dispensers received seven times more bird-pecks than those near the solvent dispensers. This suggested that the birds were somehow being attracted by the scent (there's some uncertainty regarding whether or not the animals have an actual sense of smell), and then visually hunting down the caterpillars.

The scientists now plan on using time-lapse cameras to assess what types of birds are being attracted, in different types of environments. Ultimately, their findings could result in a system that utilizes synthetic compounds to attract insectivorous birds to crops, where they will find and eat insects before they become a problem.